Storage area networks or SANs facilitate sharing of storage devices with one or more different host server computer systems and applications. Fiber channel switches (FCS) connect host servers with storage devices creating a high speed switching fabric. Requests to access data pass over this switching fabric and onto the correct storage devices through logic built into the FCS devices. Host servers connected to the switching fabric can quickly and efficiently share blocks of data stored on the various storage devices connected to the switching fabric.
Storage devices can share their storage resources over the switching fabric using several different techniques. Port zoning shares the storage resources by limiting host server access to different port connections of the SAN. For example, port zoning can direct the higher frequency host servers to higher performance storage devices on the SAN while lower frequency host servers are given lower performance storage devices on the SAN. Storage resources can also be shared using storage controllers performing various types of storage virtualization. These virtualization controllers can make one or more physical disks appear as one or more logical units or LUNs. Some virtualization controllers are limited to virtualizing the same type of drive, drives from the same manufacturer, or drives with other common characteristics.
Unfortunately, accessing these shared storage devices can be difficult if one or more host servers use too much bandwidth over the switched fabric. Servers accessing their storage over the switched fabric more frequently may use a majority of the available bandwidth and leave little or no bandwidth resources for other host server devices. Even a host server given access to higher performance storage devices may experience poor performance because the bandwidth is in use by other host servers.
Current SAN and switching devices cannot adequately monitor and allocate bandwidth provided over the switched fabric. They do not carefully monitor bandwidth utilization over the switched fabric and thus cannot assure a host server or user that storage allocated on the SAN can be accessed consistently. This lack of control over the bandwidth allocation on the switched fabric makes it difficult to provide storage resources with a high degree of reliability.
Without bandwidth monitoring and allocation capabilities, it is also hard to charge for using bandwidth to access storage over the switched fabric. In a corporate setting, the information technology (IT) department cannot accurately charge-back for information technology costs on a departmental profit and loss basis. For example, a department with a small amount of SAN storage may access the storage more frequently and use a larger amount of bandwidth than other departments with larger amounts of storage that access the storage more infrequently. Similarly, Internet Service Providers (ISP) and other companies providing commercial storage resources cannot accurately charge their customers for storage costs. Essentially, this makes it difficult for commercial companies to pass along the proper costs to the customers using more bandwidth without penalizing those using less bandwidth over the switched fabric to access their storage resources.